Recently, systems for controlling the behaviors of a vehicle have been highly developed. For example, in order to control the angle of the headlamps of a vehicle, some of such systems make use of information that predicts a turn of the vehicle. Conventionally, as a technique for an in-vehicle system to predict a vehicle turn, the technique described in publication JP-A-H11-198714 is known. According to an example described in this publication, the road shape data recorded in a navigation device or the shape of a white line detected through lane recognition is used so that the in-vehicle system is ensured to predict whether the vehicle will make a turn afterward.
However, the information on the road shape or the white-line shape is not necessarily constantly acquired. Acquirement of more highly accurate information on turn prediction has been sought for.